Li metal batteries have won the fame for the enlarged cell potential and higher theoretical specific capacity. Nevertheless, the commercial implementation is still confronted with inevitable Li dendritic growth and depressed Coulombic efficiency. The Li + transfer behavior is the vital factor to ameliorate the durability of solid electrolyte interphase (SEI). Herein, a self-exfoliated TpTG covalent organic framework (COF) was developed to construct an artificial SEI film. The versatile cationic-skeleton of TpTG could spontaneously drive the formation of nano-mesh with thickness of 3∼6 nm, and facilitate uniform dispersibility on the Li metal surface. Moreover, the 7 Li solid-state nuclear magnetic resonance spectra, Fourier-transform infrared spectra, and density functional theory calculations have identified the energetic lithiophilicity and TFSI – repulsion features. The Cl – coordinated TpTG endowed with abundant lithiophilic sites can reconfigure the charge distribution and expedite the uniform Li + migration adjacent to the electrode|electrolyte interface. The uniform Li + flux distribution redounds to reversible lithium stripping/plating and tames the dendrite formation especially at high-rate protocols. The overwhelming evidences of lower polarization, prolonged lifespan, and compact Li deposition, corroborate the practicability of self-exfoliated TpTG to achieve the goal of high-energy-density Li metal batteries.
Jingguang Yi,Dan Zhou,Yuhao Liang,Hong Liu,Haifang Ni,Li-Zhen Fan
All-solid-state lithium batteries (ASSLBs) employing sulfide electrolyte and lithium (Li) anode have received increasing attention due to the intrinsic safety and high energy density. However, the thick electrolyte layer and lithium dendrites formed at the electrolyte/Li anode interface hinder the realization of high-performance ASSLBs . Herein, a novel membrane consisting of Li 6 PS 5 Cl (LPSCl), poly(ethylene oxide) (PEO) and Li-salt (LiTFSI) was prepared as sulfide-based composite solid electrolyte (LPSCl-PEO3-LiTFSI) (LPSCl:PEO = 97:3 wt/wt; EO:Li = 8:1 mol/mol), which delivers high ionic conductivity (1.1 × 10 −3 S cm −1 ) and wide electrochemical window (4.9 V vs. Li + /Li) at 25 °C. In addition, an ex-situ artificial solid electrolyte interphase (SEI) film enriched with LiF and Li 3 N was designed as a protective layer on Li anode (Li(SEI)) to suppress the growth of lithium dendrites. Benefiting from the synergy of sulfide-based composite solid electrolyte and ex-situ artificial SEI, cells of S-CNTs/LPSCl-PEO3-LiTFSI/Li(SEI) and Al 2 O 3 @LiNi 0.5 Co 0.3 Mn 0.2 O 2 /LPSCl-PEO3-LiTFSI/Li(SEI) are assembled and both exhibit high initial discharge capacity of 1221.1 mAh g −1 (135.8 mAh g −1 ) and enhanced cycling stability with 81.6% capacity retention over 200 cycles at 0.05 C (89.2% over 100 cycles at 0.1 C). This work provides a new insight into the synergy of composite solid electrolyte and artificial SEI for achieving high-performance ASSLBs .
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